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Chapter 1: Welcome to Linux

Chapter 1: Welcome to Linux. An intro to UNIX-related operating systems. In this chapter …. History of Unix GNU-Linux Why Linux?. Long ago, in a galaxy far away …. Computing power was costly UNIVAC cost $1 million CPU time was a premium

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Chapter 1: Welcome to Linux

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  1. Chapter 1: Welcome to Linux An intro to UNIX-related operating systems

  2. In this chapter … • History of Unix • GNU-Linux • Why Linux?

  3. Long ago, in a galaxy far away … • Computing power was costly • UNIVAC cost $1 million • CPU time was a premium • Most mainframes had less computing power than a calculator on the shelf at Wal-Mart • Jobs were submitted into a queue • Only one process at a time – scheduling nightmare

  4. What was needed • Allow multiple users to access the same data and resources simultaneously • Service many users more cheaply than buying each their own machine • The ability to run multiple processes at once • And do so while maintaining user segregation and data integrity

  5. Enter Unix, pride of Bell Labs • Originally written in PDP-7 assembly language by Ken Thompson • To make it work on multiple architectures (portable), Thompson rewrote Unix in B • Dennis Ritchie developed C, and with Thompson, rewrote Unix in C

  6. What was so great about it? • Multiuser • Multiprocess • Non-proprietary • Economical for business • Initially given for free to colleges and universities (great tactic!)

  7. Descendents and bastards … • Started at Bell Labs • Picked up and continued by AT&T (SVR4) • UC Berkeley derives BSD • Sun Solaris • IRIX • Minix, XINU • Linux

  8. What happened? • UNIX became commercialized • Proprietary code, specialized distributions • Costs started to become a hindrance • So … let’s make our own Unix …

  9. GNU • Richard Stallman decides that there should be a free version of Unix available • Forms the GNU project – GNU’s Not Unix • Writes all of the system programs and utilities to mimic Unix variants • Everything but a kernel (Hurd)

  10. Final piece • Universities trying to teach Unix and OS design can’t afford Unix • Andrew Tanenbaum writes Minix • Linus Torvalds, dissatisfied with Minix, writes his own – Linux

  11. GNU-Linux • Torvalds has a perfectly functioning kernel – but no system programs • Finds a perfect candidate in GNU • Together, the operating system world was changed dramatically

  12. Free you say? • GNU-Linux is free … • Free as in speech, not free as in beer • Free to view, copy, modify, and release • Profit still to be had from packaging, support, and additional original code

  13. Why Linux? • Software • Hardware • Portability • Standards • $$$

  14. Software • An almost limitless library of programs • Applications, services, utilities • Many free, some commercial • Source code often available along with pre-built binaries

  15. Hardware • Supports thousands of peripherals and pieces of hardware • Multi-platform: x86, PPC, Alpha, SPARC, MIPS, 64-bit, SMP (multiproc systems) • Emulation of hardware for testing and development

  16. Portability • Entire operating system written in C • Shared system libraries available for all supported architectures • Code written on one platform can be compiled on any system with minimal, if any, tweaks

  17. Standards • Much of GNU-Linux already meets POSIX (Portable Operating System Interface for Computer Environments) and Unix System V Interface Definition (SVID) • Standardized for commercial and government use

  18. And don’t forget … • It’s free! (or at least really cheap!) • That’s why Linux is often the operating system of choice to teach OS design and Unix courses • We’ll be using RedHat Enterprise Linux 4 – not free but a fraction of the cost of Unix

  19. Features Overview • Multiuser • Multiprocess / Multitasking • Hierarchical Filesystem • BASH Shell command line interface / programming language • Many useful utilities built-in • Rich networking support

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